Low impedance electric connector

ABSTRACT

A low impedance, spring loaded electric connector which comprises a cylindrical body receiving a conductive wire, a plunger guided by the body and having a tip for electrically contacting with an external conductive surface, a spring compressed between the body and the plunger. The plunger can slide along the body, and is biased by the spring to assure reliable contact with the conductive surface. This connector, further, includes a resilient and conducting cantilever making sliding contact between the plunger and the body for establishing an electric path bypassing the spring. The cantilever may be formed as a portion of the plunger, or alternatively may be made as a separate one attached to the plunger or the body.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention pertains generally to an electric connector. Morespecifically, the present invention pertains to a spring loaded electricconnector having low and constant impedance, for connecting electricalsignals.

2. Description of the Prior Art

In electrical communication devices such as radio transceivers ortelephones, a universal connecting system is used for connecting betweena main body and a speaker-microphone. The universal connecting systemcan be used also for connecting a radio transceiver to other remotedevices. For example, some kind of portable radio transceiver may bechanged to a car radio transceiver by connecting the portable radio to acommunication device mounted in a car via such universal connectingsystem. Such universal connecting system, in general, comprises a malemulti-connector and a female multi-connector. The male multi-connectorincludes a plurality of pin type connectors, and the femalemulti-connector includes a plurality of surface type connectors.

An example of such a conventional pin type connector is shown andgenerally indicated at 10, in FIG. 1. Plural pin type connectors likethis are mounted together onto a mounting panel to constitute one malemulti-connector. The conventional pin type connector 10 comprises,basically, a hollow cylindrical body 20, a plunger 30 contained in andprojected from the body, a wire 50 attached to the body and a coilspring 40 positioned within the body (cf. FIG. 2). Pin type connector 10is pressed against a corresponding surface type connector 60 to makeelectrical contact between a tip 32 of plunger 30 and surface 60.Plunger 30 can slide along body 20 and is biased by coil spring 40toward an extended position in order to assure positive contact. Anelectrical current passes from surface 60 and plunger 30, through thecoil spring 40, to wire 50.

However, a coil spring has high inductance because of its spiral figureand has resistance due to its wire length. These high inductance andresistance are undesirable to electric signals, especially toalternating current signals. This high inductance and resistanceproblem, that is, high impedance problem is very serious in transmittinghigh frequency signals, such as RF signals. Additionally, the inductanceinherent in the coil varies depending on the coil length which isdetermined by the displacement of the plunger. This inductance change isa nuisance and badly affects the signal transmission through theconnector.

SUMMARY OF THE INVENTION

It is accordingly an object of the present invention to provide a springloaded electric connector having low impedance.

Another object of the present invention is to provide aspring loadedelectric connector whose inductance is constant.

The foregoing and other objects are achieved by a connector according tothe present invention, which comprises:

a cylindrical body adapted to receive an electrically conductive wireattached thereto for electrical connection to an electrical circuit;

a plunger guided by said body and slidingly movable between an extendedposition and a retracted position relative to said body, said plungerhaving a tip for making electrical contact with a conductive surfaceexternal to said body;

spring means interposed between said body and said plunger for biasingsaid plunger toward the extended position; and

cantilever means adapted to make electrical sliding contact between saidplunger and said body so as to establish an electrical pathshort-circuiting spring means.

In accordance with the aspect of the present invention, the electricalpath established by the sliding contact of the cantilever bypasses thespring, and therefore, can significantly reduce the impedance(resistance and inductance) of the connector.

Other objects, aspects and advantages of the present invention willbecome apparent to one skilled in the art from the following descriptionand the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the present invention will now be described by way ofexample and with reference to the accompanying drawings.

FIG. 1 is a perspective view of a miniature pin type electric connectorinto which the present invention may be incorporated.

FIG. 2 is a partially cross-sectional side view of the connector shownin FIG. 1, illustrating how the connector is used to complete a circuit.

FIG. 3 is an enlarged axial cross-sectional view of an electricconnector according to one embodiment of the present invention,illustrating a cantilever formed as a portion of a plunger.

FIG. 3A is a schematic cross-sectional view similar to FIG. 3,illustrating another embodiment of a cantilever.

FIG. 4 is an enlarged cross-sectional view of another embodiment of thepresent invention, illustrating a separate sleeve type cantileverattached to an outer wall of a plunger.

FIG. 5 is a similar cross-sectional view of still another embodiment ofthe present invention, illustrating a separate sleeve type cantileverattached to an inner wall of a cylindrical body.

FIG. 6 is a similar cross-sectional view of a further embodiment of thepresent invention, illustrating a separate sleeve type cantileverattached to a body and elongated up to a stopper.

FIG. 7 is a simplified cross-sectional side view of a connectoraccording to a still further embodiment of the present invention,illustrating a tubular plunger encircling a body.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings, the same reference numerals designate thesame or corresponding parts throughout the several views. FIG. 1 shows aperspective view of a miniature pin type electric connector 10, intowhich the present invention may be incorporated.

FIG. 3 illustrates an enlarged cross-sectional view of an electricconnector 10 according to one embodiment of the present invention.Connector 10 basically consists of a hollow cylindrical body 20, and aplunger 30A and a coil spring 40 contained within body 20.

The upper end 25 of tubular body 20 is open. At the periphery of thelower end of body 20, a larger diameter portion 21 is provided to form ashoulder 22. A mounting panel 90 presses shoulder 22 downward whenconnector 10 should be set on a desired place as described hereinbelow.The lowest end of body 20 has a circular opening 27. The diameter ofopening 27 is smaller than that of the inner wall 28 of hollowcylindrical body 20. And a shoulder portion 26 is formed inside of body20. Body 20 is, preferrably, made of metallic material. Alternatively,body 20 may be formed of synthetic resin such as plastic, covered withmetallic layers, at least on its inner wall. Body 20 is inserted andfixed in a hole 92 of mounting panel 90. Mounting panel 90 has aplurality of such holes (not shown), each of which receives one pin typeconnector.

A solid stopper 24 having a circular cross-section is capped to theupper open end 25 of body 20. Stopper 24 receives an electricallyconductive wire 50, for electrical connection between the connector andanother remote device or circuit. Preferrably, stopper 24 is made ofmetallic material. Alternatively, stopper 24 may be formed of syntheticresin covered with metallic layers.

Plunger 30A is generally cylindrical and consists of a tubular upperhalf and a solid lower half. The upper half of plunger 30A has a largerouter diameter and has a recessed portion 34 inside thereof. The lowerhalf of plunger 30A has a diameter smaller than the outer diameter ofthe upper half. This difference in diameter between both halves forms ashoulder portion 36. The diameter of the lower half of plunger 30A isslightly smaller than the inner diameter of opening 27 of body 20. Thelowest end of the lower half of plunger 30A is a semi-spherical tip 32for connecting with an external electrode. Plunger 30A can slide upwardand downward relative to body 20. When plunger 30A moves downward, thelower half of plunger 30A passes through opening 27 of body 20 and tip32 of plunger 30A protrudes out of the lowest end of body 20 (extendedposition). In this extended position, tip 32 of plunger 30A canelectrically contact with an electrode 60 which is an electricallyconductive surface formed on top of a plate 62 external to body 20.Shoulder portion 36 of plunger 30A and shoulder portion 26 of body 20cooperate to limit the downward movement of plunger 30A, even whensurface 60 does not exist below tip 32. On the other hand, tip 32withdraws (retracted position), when plunger 30A goes upward. Plunger30A is, preferrably, made of resilient metallic material. Alternatively,plunger 30A may be formed of elastic resin covered with electricallyconductive material.

Coil spring 40 is, generally, interposed between body 20 or stopper 24and plunger 30A. More specifically, the upper end of compression spring40 contacts the bottom face of stopper 24, and the lower end of spring40 is received in recess portion 34 of plunger 30A. Coil spring 40 doesnot need to be electrically conductive. Plunger 30A is always biaseddownward (in the direction of the extended position) by the force ofcoil spring 40 compressed between stopper 24 and plunger 30A. Therefore,the restoring force of coil spring 40 assures that tip 32 is alwayscontacting with surface 60 of plate 62 with great reliability, andreduces an ohmic resistance through the contact between tip 32 andsurface 60.

The upper edge or rim 35A of the upper half of plunger 30A is bent orcurved radially outward to form a cantilever 70A. Cantilever 70A iscontacting the inner wall 28 of tubular body 20. Because plunger 30A hasresiliency, cantilever 70A is always pressing againt and never detachedfrom the inner wall of body 20 throughout the sliding movement ofplunger 30A. Therefore, cantilever 70A makes reliable electrical contactbetween plunger 30A and body 20. Alternatively, a spring cantilever 70A'may riveted or spot welded to an upper surface of plunger 30A' as shownin FIG. 3A. In this case, reliable electrical contact between plunger30A' and body 20 is also obtained.

In operation, when mounting panel 90 is placed over and aligned withplate 62, tip 32 is positioned right on conductive surface 60, andpressed against it to make electrical contact. Thus connector 10according to this embodiment of the present invention establishes anelectrical path which is from conductive surface 60, through tip 32,cantilever 70A, body 20 and stopper 24 to wire 50, bypassing orshort-circuiting coil spring 40. This electrical path passing throughcantilever 70A has low resistance less than that of the prior electricalpath passing through the coil, because the distance of the path throughthe cantilever is shorter than that of the conventional coil path.Besides, whereas a coil has very high inductance, the electrical paththrough the cantilever has little inductance. Thus the connectoraccording to the present invention has significantly reduced itsimpedance. Additionally, the inductance of the electrical path throughthe cantilever does not vary even while the plunger moves up and down.Therefore, the connector according to the present invention provides lowand constant impedance property which is very advantageous toalternating current signals, especially to RF signals.

FIG. 4 shows another preferred embodiment of the present invention inwhich a separate sleeve type cantilever 70B is attached to the outerwall 38 of plunger 30. Cantilever 70B is, preferrably, made of resilientand electrically conductive material. Alternatively, cantilever 70B maybe formed of elastic resin covered with a conductive layer. Cantilever70B consists of a lower proximal portion 72B and an upper distal portion74B. Straight proximal portion 72B is actually fixed to outer wall 38 ofplunger 30 by some means such as press fitting and electricallyconnected to it. Distal portion 74B is curved or bent from proximalportion 72B radially outward, and is slidingly contacting with the innerwall 28 of tubular body 20 to make electrical contact with it. Theelectrically conductive and resilient properties of cantilever 70Bassure reliable electrical connection between plunger 30 and body 20.Thus connector 10 of this embodiment establishes an electrical pathsimilar to that shown in FIG. 3. The electrical path of this embodimenthas low resistance and low and constant inductance, and therefore lowand constant impedance.

FIG. 5 shows still another embodiment of the present invention in whicha separate sleeve type cantilever 70C is attached to the inner wall 28of body 20. Cantilever 70C is, preferrably, made of resilient andelectrically conductive material. Alternatively, cantilever 70C may beformed of elastic resin covered with a conductive layer. Cantilever 70Cconsists of an upper straight proximal portion 72C and a lower curveddistal portion 74C. Proximal portion 72C is actually fixed by some meanssuch as press fitting to inner wall 28 of body 20 and electricallyconnected to it. Distal portion 74C is curved or bent from proximalportion 72C radially inward, and is contacting with the outer wall 38 ofplunger 30 to make electrical contact with it. The electricallyconductive and resilient properties of cantilever 70C assure reliableelectrical connection between plunger 30 and body 20. Thus connector 10of this embodiment also establishes an electrical path similar to thatshown in FIG. 3. The electrical path of this embodiment has low andconstant impedance.

FIG. 6 shows a further embodiment of the present invention which issimilar to the previous embodiment shown in FIG. 5, but has onesignificant difference from the FIG. 5 embodiment. The difference in theembodiment of FIG. 6 is that an upper proximal portion 72D of acantilever 70D is elongated enough to reach a stopper 24. The elongatedportion 76D of cantilever 70D contacts with and electrically connects tostopper 24 which is also electrically conductive. Connector 10 accordingto this embodiment shown in FIG. 6 establishes a simplified electricalpath which is from conductive surface 60, through tip 32 and cantilever70D, and directly to stopper 24 and wire 50 (bypassing body 20).Therefore, body 20 of this embodiment is not required to be electricallyconductive. Thus, the connector of the FIG. 6 embodiment providesespecially low resistance, and therefore low and constant impedance.Alternatively, stopper 24 and cantilever 70D may be formed as one solidintegral conductive material, instead of two parts. In this case,further low resistance can be achieved because of no contact resistancebetween the two parts.

FIG. 7 illustrates an enlarged cross-sectional view of an electricconnector 10 according to a still further embodiment of the presentinvention, in which a solid cylindrical body 20E is inserted into atubular plunger 30E. Connector 10 basically consists of a hollowcylindrical plunger 30E, and a solid cylindrical body 20E and a coilspring 40 contained within plunger 30E.

The upper end of body 20E receives an electrically conductive wire 50,for electrical connection between the connector and an other remotedevice or circuit. At the middle of body 20E, formed is a flange 22E tobe forced downward by a mounting panel 90E. The lower portion of body20E is inserted into cylindrical plunger 30E. The lowest end of body 20Ehas a flange 36E which prevents plunger 30E from falling off. Body 20Eis, preferrably, made of metallic material. Alternatively, body 20E maybe formed of synthetic resin such as plastic, covered with metalliclayers. Body 20E is inserted and fixed in a mounting panel 90E.

In this embodiment, stopper 24 as shown in FIG. 3 is not required.

Plunger 30E is hollow cylindrical and consists of a tubular upper halfhaving a large diameter, and a solid lower half having a smallerdiameter. The lowest end of plunger 30E is a semi-spherical tip 32 forconnecting with an electrically conductive surface 60 external to body20E. Plunger 30E can slide and move upward (toward a retracted position)and downward (toward an extended position) along body 20E. In theextended position, tip 32 of plunger 30E can electrically contact withsurface 60. Plunger 30E is, preferrably, made of resilient metallicmaterial. Alternatively, plunger 30E may be formed of elastic resincovered with electrically conductive material.

Coil spring 40 is, generally, interposed between body 20E and plunger30E. More specifically, the upper end of compression spring 40 contactsthe bottom face of body 20E, and the lower end of spring 40 sits on aninner bottom surface of plunger 30E. Coil spring 40 does not need to beelectrically conducting. Plunger 30E is always biased downward (in thedirection of the extended position) by the force of coil spring 40compressed between body 20E and plunger 30E. Therefore, the restoringforce of coil spring 40 assures that tip 32 is always contacting withconductive surface 60 with great reliability, and reduces an ohmicresistance through the contact.

The upper edge or rim 35E of the upper half of plunger 30E is bent orcurved radially inward to form a cantilever 70E. Cantilever 70E iscontacting an outer wall 28E of body 20E. Because plunger 30E hasresiliency, cantilever 70E is always pressing against and never detachedfrom outer wall 28 of body 20E throughout the sliding movement ofplunger 30E. Therefore, cantilever 70E makes reliable electrical contactbetween plunger 30E and body 20E. Thus connector 10 according to thisembodiment of the present invention establishes an electrical path whichis from the conductive surface, through tip 32, cantilever 70E and body20E to wire 50 short-circuiting coil spring 40. This electrical paththrough cantilever 70E has low resistance less than that of theelectrical path through the coil, because the distance of the paththrough the cantilever is shorter than the coil path distance. Besides,whereas a coil has very high inductance, the electrical path through thecantilever has low inductance. Additionally, the inductance of theelectrical path through the cantilever does not change even while theplunger moves up and down. Thus the connector of this embodiment canprovide low and constant impedance.

While the present invention has been particularly set forth in terms ofspecific embodiments thereof, it will be understood in view of theinstant disclosure, that numerous variations upon the invention are nowenabled to those skilled in the art, which variations yet reside withinthe scope of the present teaching. Accordingly, the invention is to bebroadly construed, and limited only by the scope and spirit of theclaims now appended hereto.

We claim:
 1. A low impedance, spring loaded connector for connectingelectrical signals, comprising:a cylindrical body adapted to receive anelectrically conductive wire attached thereto for electrical connectionto an electrical circuit; a plunger guided by said body and slidinglymovable between an extended position and a retracted position relativeto said body, said plunger having a tip for making electrical contactwith a conductive surface external to said body; spring means interposedbetween said body and said plunger for biasing said plunger toward theextended position; and cantilever means adapted to make electricalsliding contact between said plunger and said body so as to establish anelectrical path short-circuiting said spring means and the electricalpath so established providing a constant low resistance and inductancepath independent of the state of the spring means.
 2. A low impedance,spring loaded connector as claimed in claim 1, wherein said cantilevermeans is formed as a portion of said plunger by bending a portion ofsaid plunger to slidingly contact a surface of said body.
 3. A lowimpedance, spring loaded connector as claimed in claim 1, wherein saidplunger is received within said cylindrical body and generally axiallymovable relative to said cylindrical body.
 4. A low impedance, springloaded connector as claimed in claim 1, wherein said plunger receivessaid cylindrical body therewithin and generally axially movable relativeto said cylindrical body.
 5. A low impedance, spring loaded connector asclaimed in claim 3, wherein said cantilever means comprises a separatecylindrical sleeve positioned between said cylindrical body and saidplunger.
 6. A low impedance, spring loaded connector as claimed in claim5, wherein said cylindrical sleeve is fixed onto an outer surface ofsaid plunger, and a portion of said sleeve is bent to slidingly contactan inner surface of said cylindrical body.
 7. A low impedance, springloaded connector as claimed in claim 5, wherein said cylindrical sleeveis fixed onto an inner surface of said cylindrical body, and a portionof said sleeve is bent to slidingly contact an outer surface of saidplunger.
 8. A low impedance, spring loaded connector as claimed in claim7, wherein said cylindrical body is provided with a stopper fixed to oneend thereof, said stopper being formed to receive an end of theelectrically conductive wire therein.
 9. A low impedance, spring loadedconnector as claimed in claim 8, wherein said stopper has anelectrically conductive surface making electrical contact with the wireand another electrically conductive surface making contact with saidcylindrical sleeve, and said cylindrical sleeve is formed ofelectrically conductive material and establishes an electrical path fromsaid plunger through the electrically conductive surfaces of saidstopper to the wire.
 10. A low impedance, spring loaded connector asclaimed in claim 5, wherein said cylindrical sleeve is formed ofresilient metallic material.